With the advent of long duration incoherent scatter radar experiments measuring ionospheric plasma convection over a wide range of latitudes and at all local times, the mapping and study of the spatial and temporal distribution of electric fields within the magnetosphere becomes possible. We consider the problems of mapping the ionospheric electrostatic potential distribution into the magnetosphere under the assumption that magnetic field lines are electrostatic equipotentials. We address the practical problem of developing a mapping technique which can adequately project ionospheric observations, acquired at different geographic longitudes, into the magnetosphere. The mapping must include the effects of a magnetotail when considering auroral latitudes and is a function of diurnal and seasonal effects and is ionospheric longitude dependent. Mapping observed ionospheric potential distributions into the magnetosphere yields parameters such as: the distribution of electric fields in the magnetosphere, the cross tail potential, the location of plasmapause, the local time of the ‘stagnation’ bulge region and the gradients of the electric field in the vicinity of the plasmapause.